The invention relates to a plasma source that combines the advantages of inductively coupled plasma and capacitively coupled plasma.
Inductively coupled plasmas (ICP) reach a high ion density with low plasma potential. Furthermore, large area plasmas can also be created. In combination with plasma generation that is especially simple, this makes an economical method of operation of the plasma sources possible.
Capacitively coupled plasmas (CCP) have a lower ignition temperature because of the lower excitation and rotation temperatures. Due to the ease of handing and the stability, capacitively coupled plasma can be used for a multitude of applications, among them in aerosols or wet gasses, in which other plasmas would be extinguished under certain circumstances. CCP coupling is especially well suited to accelerate ions in the plasma and extract them for processing.
Both types of plasma generation consequently have their advantages and reasons for existing in the technology.
An ICP source is described in DE 103 58 505 B4 that has a magnetic pole shoe arrangement; the exciter coils are arranged in grooves of the pole shoes. The pole shoes bring about a concentration of the magnetic fields of the exciter coils below the pole shoes in the area intended to be used for plasma ignition. Further permanent magnets are provided in the form of a multi-pole magnet arrangement on both sides and extending linearly with respect to the magnetic pole shoes. The magnetic fields of the multi-pole arrangement are superimposed on the inductively coupled plasma in this layout. The layout that is described is especially suitable for elongated, flat plasma sources, as used as a preference for solar-cell production with a continuous processing method.
EP 0 908-923 B1 describes a plasma source in which the magnetic core (ferrite core), which serves to concentrate the magnetic field in the plasma chamber, is also simultaneously used as a closure for the connector opening of the plasma source to the processing chamber. Preferred embodiments of the plasma source are rotationally symmetric. No multi-pole magnet arrangements are used to generate Whistler waves in the plasma.
Known designs of ICP sources do not have the advantageous characteristics of CCP sources.
The problem therefore arises of creating a plasma source that unites the advantages of the ICP and CCP plasmas.